Over the years, since the first introduction of man-made fibers into the textile industry, there has been an almost ceaseless quest for different techniques to make such man-made synthetic fibers appear like and be similar to natural fibers (e.g. cotton and wool). As part of this, most procedures have as at least part of the objective the increasing bulk of such man-made fibers in order to provide garments made therefrom with a soft, luxuriant hand, sufficient elasticity to provide a good fitting garment, increased moisture absorption for better wearing comfort and increased yarn volume to allow for more coverage.
The process of texturing or crimping in order to impart random loops or otherwise modifying continuous filament yarns to increase their cover, resilience, abrasion resistance, warmth, insulation and moisture absorbance or to provide a different surface texture can be broken down roughly into six main groups. These include air-jet texturing, edge crimping, false-twist texturing, gear crimping, knit-de-knit texturing and stuffer box crimping.
With the advent, however, of biconstituent yarns which are in effect self-crimping, an additional method of forming man-made yarns into textured-type products has evolved. One example of such a yarn is DuPont's N-780, now referred to as type #207, a side-by-side biconstituent yarn. Another example is Monvelle produced by Monsanto. This type of yarn is extremely sensitive to the application of heat and has an extremely high shrinkage rate characteristicly approaching 76%. Products produced from this yarn, after proper finishing exhibit very good anti-snagging or picking characteristics and thus is considered to be an extremely acceptable yarn for use in the production of ladies' hosiery.
While the yarn manufacture indicates and practice shows it to be possible to produce greige products directly from this yarn, one of the major drawbacks with employing such self-crimping yarns is that garments or fabrics produced therefrom have to be made in an extremely large size proportionialized according to the shrinkage characteristics of the yarn. If done correctly when the garments or materials are subjected to heat during dyeing and finishing, the shrinkage will bring the garments or fabrics to a proper size and at the same time develop the crimp and anti-snag characteristics of the yarn.
The theory of using such yarns has not worked well in practice at all times and there are several disadvantages to working with such yarn. In some instances production equipment would have to be modified to produce the necessarily oversized fabric or garment. It is somewhat difficult to gauge how large garments should be to produce predetermined sizes with the exactness required by today's consumers and, in fact, a fair amount of guess work is required before full-scale processing of such garments can be undertaken. This is quite inconvenient, especially when there are size changes or different stitch configurations which would cause variations in the amount of yarn being used which affect the ultimate size being obtained. The pick resistance of the oversized garment is extremely fragile and because the fabric made is so loose, it is extremely easy to have yarns somehow become damaged thereby producing an inordinately large number of seconds. On many occasions, one out of every three garments is lost between production and heat treating.
In view of such problems attendant to the use of this yarn, it was desired to be able to properly develop crimp in the yarn and to reduce the size of the yarn such that garments or fabrics could be made "to sizes" with any subsequent finishing or heating finishing operations serving to only develop even additional crimp in the yarn thereby improving the anti-snag properties of the yarn rather than altering the size of those fabrics or garments.
The knit-de-knit process as it is conventionally known is exemplified in the Page patent, U.S. Pat. No. 2,601,451. This patent relates to a method of making a stocking and has as one specific object the production of yarn through a knit-de-knit procedure. The patent discusses the problem called phasing with respect to the construction of hosiery items which occurs when there is a substantial correspondence between the frequency of the reoccurrence of the crimps in the formed yarn and the frequency of reoccurrence of the final knitted loops. Where these two frequencies tend to fall into phase, undesirable lines will appear usually referred to as phasing. Thus, any process for producing crimped yarn must be accomplished at a frequency where the reoccurrence of the crimps when used to make fabrics will not create phasing problems. The Page patent indicates that a standard 400-needle circular knitting machine is used to knit a tube of material which can be stretched to a circumference of 161/2 inches or 30 inches. The knit tube is subsequently subjected to a shrinking or setting action at a temperature ranging between 225.degree. F. to 250.degree. F. Thereafter, the knit tube is unraveled and the yarn used in the production of garments. It should be pointed out, that the type of crimped yarn resulting from employing the process set forth in the Page patent would have a regular pattern of successive and uniformly spaced crimps, each of which would have the configuration of a knitted stitch loop.
A modification of the knit-de-knit process set forth in the Page patent is described in the Silver et al. patent, U.S. Pat. No. 3,330,018 dated July 11, 1967. The object of the Silver et al. patent was to obtain a crimped yarn which would include various portions of straight or uncrimped sections together with crimped sections so that when the yarn was knit or woven into a fabric, the fabric would have a novelty pattern with varying degrees of stretchability in various portions thereof. In accomplishing that objective, Silver et al. employed alternating knit and float sections with the number of needles used to form the alternating knit and float sections being variable in a random and preferably non-repeating manner.
It was found that when employing the hitherto conventional knit-de-knit crimping procedures together with conventional heat treating of the knit tubular sleeve, it would not serve to properly treat the bicomponent self-crimping yarn in a manner that would make it suitable for use as a conventional yarn in producing "to size" fabrics or garments.